Design of a low-cost system for the measurement of the radial displacements of a cylindrical metal target

This study presents the design and implementation of a low-cost system for measuring the radial displacement of a cylindrical metal target using inductive sensors and flexible planar coils. The proposed approach leverages three planar coils arranged circumferentially around the target, combined with low-cost inductance-to-digital converters (LDCs), to achieve submicrometric resolution and high sampling rates. The methodology enables accurate determination of radial displacement and the position of the target's center by processing inductance variations caused by changes in distance between the coils and the target. A reconfigurable test bench was developed, incorporating a stepper motor for precise linear movement and a high-accuracy laser displacement sensor for calibration. Calibration tests were conducted to characterize the system, evaluate its uncertainty, and validate the proposed method. Preliminary results demonstrate the feasibility of the system and its ability to estimate radial displacement with measurable uncertainty. Further improvements in accuracy could be achieved by integrating resistance (RP) and inductance (L) measurements with optimization algorithms for multi-output calibration. This low-cost solution shows potential for applications in vibration monitoring and precision engineering tasks requiring high-resolution displacement measurements.